The new Australian import “Wolf Creek” plays like a collision between two of the more popular conceits of contemporary horror films. The first half deals with a small group of know-it-alls who somehow find themselves stranded in the middle of nowhere and realize with horror that their book smarts and snarky attitudes are completely useless in such a situation. The second has those same people being picked off, one by one and in the most sadistic manner possible, by a virtual stranger who seems to have made up for his lack of motivation with an abundance of hunting rifles, giant knives and other handy torture devices. In other words, imagine a peanut butter cup of terror in which “The Blair Witch Project” gets dipped into the original “The Texas Chain Saw Massacre” and then smeared with Vegemite.

After the requisite title cards informing us that a.) 30,000 people go missing in Australia each year and b.) that what we are about to see is “based on a true story,” the film opens on a trio of amiable young dopes–British girls Liz (Cassandra Magrath) and Kristy (Kestie Morassi) and Aussie bloke Ben (Nathan Phillips)–as they set off on a long road trip through the Australian outback. They make a stop at the virtually abandoned Wolf Creek meteor crater and when they finally return to their car, they discover that both the auto and their watches have mysteriously stopped working. That evening, they are spotted by the amiable Mick Taylor (John Jarratt), a friendly Crocodile Dundee-type who offers to tow them back to his remote farm and fix the car while they spend the night. Since the kids have no real alternative and since he seems friendly enough, they agree and spend a friendly few hours around the campfire before turning in. Later on, Liz wakes up and discovers that . . . well, you can probably guess what she discovers but I wouldn’t dream of giving away anything about the particulars.

Although some gorehounds, stoked by the considerable hype that the film has received ever since its premiere at Sundance last winter (not to mention the rave quotes from the likes of Quentin Tarantino, Robert Rodriguez and the dope behind “Saw II”), may complain that “Wolf Creek” takes too long to get to the more visceral material–nearly two-thirds of the film has elapsed before the gore kicks in–it is this section of build-up that is actually more authentically creepy than the blood-soaked payoff. The most convincing horror films have always based their chills on authentic human emotions–the shower scene in “Psycho” continues to have an impact today not because of the level of violence but because Hitchcock knew that people are at their most nakedly vulnerable in such a situation and mercilessly exploited that fear for maximum impact. The idea of somehow being stranded in the middle of nowhere with no apparent method of rescue or escape is both terrifying (as someone once trapped in a faulty van on the wrong side of Wyoming’s Devil’s Tower for a few hours, I can fully attest to that feeling) and universal–the only thing worse is the fact that if someone does happen along, you are basically forced to put your entire life into the hands of a total stranger and hope that they won’t somehow take advantage of your vulnerability and do you harm.

Debuting writer-director Greg McLean does such a good job of slowly and quietly building this tension during the opening half that it is a little disappointing to see him largely abandon it for the hard-core violence of the closing half. It is well-done, I suppose (though more than a little derivative of too many horror films to list here), but this is the kind of filmmaking that any hack with a big knife and a few gallons of fake blood can pull off. About the one fresh aspect in this section is the memorably malevolent performance from John Jarratt as the increasingly unhinged Mick. Virtually unknown in the US (I understand that he is quite the popular television personality in Australia), his performance is one of the more unforgettable screen psychos of recent years, mostly because McLean resists the urge to turn him into a sort of anti-hero whom we are cheering for as he bumps off his victims as we did with Jigsaw in the “Saw” films

In the end, “Wolf Creek” is more of a calling-card film for McLean to demonstrate his flair behind the camera than a decent horror film in its own right. It isn’t bad–it certainly beats the dismal likes of “Saw II” or “The Fog”–but it winds up being just a little bit too derivative in the end to really take off on its own. Horror fans might appreciate the fact that it doesn’t actively insult their intelligence but they will probably wind up mentally cataloguing the various classics that it seems to be pilfering from in virtually every scene. Oddly, I suspect that it may play better for viewers who don’t normally watch such genre films and who might not be as familiar with its sources–of course, what would such people be doing at “Wolf Creek” in the first place?